Thermodynamic analysis and optimisation of a combined liquid air and pumped thermal energy storage cycle

Abstract

Pumped thermal energy storage (PTES) and liquid air energy storage (LAES) are two large-scale electricity storage technologies that store energy in the form of thermal exergy. This is achieved by operating mechanicallydriven thermodynamic cycles between thermally insulated storage tanks. Both technologies are free from geographic restrictions that apply to pumped hydro and most compressed air storage. The present paper describes a novel, combined system in which PTES operates as a topping cycle and LAES as a bottoming cycle. The fundamental advantage is that the cold thermal reservoirs that would be required by the two separate cycles are replaced by a single heat exchanger that acts between them, thereby saving significant amounts of storage media per unit of energy stored. In order to reach cryogenic temperatures, the PTES cycle employs helium as the working fluid, while the LAES cycle uses supercritical air (at around 150 bar) which is cooled sufficiently to be fully liquefied upon expansion, thus avoiding recirculation of leftover vapour. A thermodynamic study of a baseline configuration of the combined cycle is presented and results are compared with those of the separate systems. These indicate that the new cycle has a similar round-trip efficiency to that of the separate systems while providing a significantly larger energy density. Furthermore, three adaptations of the base-case combined cycle are proposed and optimised. The best of these adaptations achieves an increase in thermodynamic efficiency of about 10 percent points (from 60 % to 70 %), therefore significantly exceeding the individual cycles in both energy density and efficiency.

Progress and prospects of thermo-mechanical energy storage—a critical review

“…Furthermore, Cetin et al [104] proposed a geothermal flash plant, in which, during peak times, additional heat is added from the geothermal resource to generate electricity. Hybrid systems combining LAES with other TMES systems, such as CAES [94,105] and PTES [95], have been proposed in literature and found to improve the round-trip efficiency of the respective standalone systems by up to 10%.…”

Energetic and Exergetic Investigation of Regenerative Gas Turbine Air-Bottoming/Steam -Bottoming Combined Cycle

“…The airbottoming combined (ABC) cycle and Steam-bottoming combined (RSBC) cycle can be replaced by the traditional power generation system because of their high performance and minimum exergy exhaust gasses losses. The power generation by this technique involves the turbine inlet temperature of topping cycle (TIT) and a mass fraction of exhaust gasses to optimize the overall cycle performance [12][13][14].…”

Levelised Cost of Storage (LCOS) analysis of liquid air energy storage system integrated with Organic Rankine Cycle

“…So far, the research interest toward LAES has been growing year by year with a significant research production mainly focused on techno-economic analysis and system optimization [9][10][11][12][13] and LAES hybridization with a possible waste heat/cold recovery integration from external/internal sources [14][15][16][17][18].…”

“…The proposed system is found to economically perform better than the respective stand-alone systems, CAES and LAES, under certain conditions (storage duration longer than 36 hours). Farres-Antunez et al [16] have proposed a hybrid energy storage system combining LAES and Pumped Thermal Energy Storage system (PTES). The hybrid system is found to increase the round trip efficiency by 10 % compared to the respective stand-alone systems.…”